Industry is beset by unwanted dust or very small particulates which either intermix with or adhere to larger particles or particulate material. In the first instance, the small intermixed particulates are not adhesively attached to the larger particulate material and therefore have a tendency to become airborne when the larger particulate material is transferred or transported. This may create an undesirable condition in that it may be unhealthy to breath the airborne particles. This concern is especially prevalent in the grain handling or milling industries and also in mining, quarrying and processing of minerals.
In the latter instance, instead of intermixing, the small particulates often adhere to the larger particulate materials by static charge, moisture or physical impingement. This typically occurs during the processing of the particulate material wherein small particulates are generated by the friction between the particles themselves or with equipment surfaces. Such an occurrence often renders the larger particulate material less suitable for its intended use. For example, in the clay industry, particulate material is prepared for a variety of uses, including for oil and grease absorption or for use as animal litter. If, during the processing of these materials, the fine particulates adhere to the larger particles, the ability of the larger particulates to absorb oil and grease or to effectively neutralize odor (in the case of animal litter) is diminished.
For purposes of the explanation which follows, the larger particulate material will be referred to as "particles" and the smaller particulate material or fines will be referred to as "particulates".
Thus, a variety of devices for separating small particulates from larger particles have been developed. These devices are generally known as dedusters. Some of these dedusters separate the different sized particles and particulates by initially moving them through interconnected chambers with air and then subsequently subjecting them to machine-operated components for the actual separation of the particles. See U.S. Pat. Nos. 4,335,151; 4,857,178. Other dedusters separate particles by a combination of abrasive impact and air movement. One device in particular is disclosed in U.S. Pat. No. 4,568,453 wherein a stream of particles and particulates cascades down a series of baffles while being exposed to a vacuum airstream which separates and removes the particles.
While the aforementioned prior art deduster devices separate some of the particulates from the larger particles, there are problems associated with their use, as explained below.
First, the known deduster devices are generally ineffective in separating small particulates that are intermixed with larger particles in that many of the small particulates are not accessible to the vacuum airstream or other removal means.
Second, the known deduster devices are also ineffective in separating particles that are adhered to one another. This may be due, in some instances, to an electrostatic charge between the particles, which usually interferes with the separation of the particles in that the electrostatically charged particles cling to adjacent particles and thereby resist the vacuum airstream. This situation is commonly a problem with devices that utilize only an airstream for particle separation. In other instances, the ineffectiveness of the known deduster devices in separating adhered particulates may be attributed to the inferior or inadequate abrasion techniques in these dedusters which do not adequately dislodge the small particulates from the larger particles for their subsequent removal.
Aside from the aforementioned problems associated with separating particulates, there are other serious drawbacks and disadvantages with the known deduster devices. For example, many known deduster devices require external energy sources for operating their various components, including mechanisms for abrading and for impacting the combined particle and particulate matter. Furthermore, the deduster devices which include external energy sources generally have elevated operation costs and generally require excessive amounts of space when assembled.
Despite the numerous disadvantages with the above-mentioned dedusting devices, they are still widely used. Thus, while these dedusting devices produce some dust-free material, they often do not effectively meet stringent dust-free standards.
Accordingly, an object of the present invention is to provide an apparatus that separates fine particulates from a particle flow and which produces substantially dust free material.
Another object of the present invention is to provide an apparatus that separates fine particulates from a particle flow by transforming the linear momentum of the combined particle and particulate flow to angular momentum thereby spreading the flow out into a fan to facilitate the separation process.
Another object of the present invention is to provide an apparatus that separates fine particulates from a particle flow without using motorized components.
Yet another object of the present invention is to provide an apparatus that separates fine particulates from a particle flow which is economical to operate and which requires a relatively limited amount of space.